Disc drive machines record and reproduce information on a recording media. The media generally takes the form of circular information storage discs having a multiplicity of concentric tracks. Conventional Winchester type disc drives include a plurality of vertically aligned rotating information storage discs, each having at least one associated magnetic head that is adapted to transfer information between the disc and an external system. Each head is carried by an elongated flexure arm. The flexure arms are vertically aligned and are each attached to a common head positioner assembly. The head positioner assembly may be either rotationally mounted, or may take the form of a linear carriage that is free to move back and forth along a single axis. In rotary mounted head positioner assemblies, a voice coil motor rotates the head positioner assembly about a pivot mechanism to precisely position the heads relative to the magnetic discs.
Due to the precise positioning requirements of the read/write heads, the head positioner assembly must be finely balanced and the pivot mechanism must offer high precision and reliability, together with low mechanical resistance, in order to minimize undesirable vibrations within the drive. New drives constantly push for higher access speed and more memory storage within a confined space. In high speed compact disc drives, such as the 31/2 inch drives now becoming popular, if any of the drive's components have primary resonant frequencies under approximately 5 Khz, mechanical movement within the drive will occasionally excite the resonant frequencies during normal operation which can limit the drives performance and/or generate undesirable noise which gives the appearance of an inferior quality product.
The pivot mechanism typically includes a pair of bearings that must be preloaded to properly balance the assembly. One problem frequently encountered in manufacturing is maintaining consistent preloads even over wide thermal variations.